The present invention generally relates to technology for generating a two-dimensional image by subjecting an event set in a virtual three-dimensional space to perspective projection transformation, and in particular relates to image processing technology capable of alleviating the computational load upon more realistically representing numerous spectators in a game device or the like relating to sports.
Pursuant to the development of computer technology in recent years, image processing technology relating to TV game machines and simulators (simulation rides) is becoming universally prevalent. In this kind of system, the rich expression of images to be displayed is key in increasing the commercial value. For instance, in a TV game machine related to sports such as tennis or soccer, it is desirable to realistically express the behavior of sports players to be operated by a player as well as realistically express the behavior of the attending spectators in order to further increase the commercial value. Meanwhile, by attempting to improve the expressiveness of images, the computational load required in generating such images tends to increase. Since TV games and the like are demanded of real-time processing for generating images, there is a certain limit in the tolerable computational load. Therefore, technology capable of alleviating the computational load without deteriorating the expressiveness is sought after.
As conventional technology trying to meet the foregoing demands, there is a method that applies technology referred to as billboard processing (refer to Non-Patent Document 1). Specifically, this method represents a target body such as spectators based on a two-dimensional model using plate-shaped polygons, appropriately rotates the plate-shaped polygons (two-dimensional models) according to a line-of-sight vector showing the line of sight of a virtual camera, and thereafter replaces the texture to be mapped to the plate-shaped polygons.
Nevertheless, even in the case of the foregoing method, since coordinate conversion processing must be performed to the coordinate components (x, y, z components of the respective apexes) or the normal line components of the four apexes of the plate-shaped polygons, the effect of alleviating the computational load is low when trying to represent numerous spectators. Therefore, technology capable of achieving further reduction of the computational load without deteriorating the expressiveness of images concerning spectators or the like is sought after.
[Non-Patent Document 1]
Shigenori Tanaka et al., “Introduction to Game Programming with DirectX: Chapter 6—Practical Game Development: 6.3.2 Billboard Drawing”, [online], Aug. 29, 2003, Microsoft Corporation, [Searched on Aug. 25, 2005] Internet <URL: http://www.microsoft.com/japan/msdn/academic/Articles/DirectX/06/>